Upload doesn't work with py39 build

[nehaljwani]

Exception is hidden, but it is:

module 'base64' has no attribute 'encodestring'

Reproduce with diff:

--- /Users/nwani/.conda/pkgs/anaconda-client-1.7.2-py_0/site-packages/binstar_client/__init__.py	2019-02-02 20:37:29.000000000 -0500
+++ /Users/nwani/.conda/envs/cf/lib/python3.9/site-packages/binstar_client/__init__.py	2021-02-16 12:32:42.000000000 -0500
@@ -526,13 +526,17 @@
         s3url = obj['post_url']
         s3data = obj['form_data']

-        if md5 is None:
-            _hexmd5, b64md5, size = compute_hash(fd, size=size)
-        elif size is None:
-            spos = fd.tell()
-            fd.seek(0, os.SEEK_END)
-            size = fd.tell() - spos
-            fd.seek(spos)
+        try:
+            if md5 is None:
+                _hexmd5, b64md5, size = compute_hash(fd, size=size)
+            elif size is None:
+                spos = fd.tell()
+                fd.seek(0, os.SEEK_END)
+                size = fd.tell() - spos
+                fd.seek(spos)
+        except Exception as e:
+            print(e)
+            raise(e)

         s3data['Content-Length'] = size
         s3data['Content-MD5'] = b64md5

[jakirkham]

Looks like this was fixed upstream in PR: anaconda/anaconda-client#551